Gas turbine engine forward bearing compartment architecture

ABSTRACT

A gas turbine engine includes a front center body case structure. A geared architecture is at least partially supported by the front center body case structure. A bearing structure is mounted to the front center body case structure to rotationally support a shaft driven by the geared architecture, the shaft drive a fan. A bearing compartment passage structure is in communication with the bearing structure through the front center body case structure. A method is also disclosed.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/939,508, filed Mar. 29, 2018, which is a continuation of Ser. No.15/865,393, filed Jan. 9, 2018, which is a continuation of U.S.application Ser. No. 15/046,524, filed Feb. 18, 2016, which is acontinuation of U.S. application Ser. No. 14/745,724, filed Jun. 22,2015, which was a continuation-in-part of U.S. patent application Ser.No. 14/640,251, filed Mar. 6, 2015, which was a continuation of priorU.S. patent application Ser. No. 13/346,832, filed Jan. 10, 2012, nowU.S. Pat. No. 9,004,849 the entirety of which is herein incorporated byreference.

BACKGROUND

The present disclosure relates to a gas turbine engine, and inparticular, to a case structure therefor.

Geared turbofan architectures may utilize epicyclic reduction gearboxeswith planetary or star gear trains for their compact design andefficient high gear reduction capabilities. The geared turbofanarchitecture de-couples a fan rotor from a low spool through thereduction gearbox which results in isolation of the forwardmost bearingcompartment.

SUMMARY

In a featured embodiment, a gas turbine engine includes a front centerbody case structure. A geared architecture is at least partiallysupported by the front center body case structure. A bearing structureis mounted to the front center body case structure to rotationallysupport a shaft driven by the geared architecture. The shaft drives afan. A bearing compartment passage structure is in communication withthe bearing structure through the front center body case structure.

In another embodiment according to the previous embodiment, the bearingstructure includes a seal.

In another embodiment according to any of the previous embodiments, thebearing structure includes a bearing.

In another embodiment according to any of the previous embodiments, thebearing compartment passage structure includes a hollow front centerbody strut.

In another embodiment according to any of the previous embodiments, thehollow front center body strut is in fluid communication with a fanrotor bearing support structure which at least partially supports thebearing structure.

In another embodiment according to any of the previous embodiments,further includes a conditioning device in communication with the bearingcompartment passage structure.

In another embodiment according to any of the previous embodiments, theconditioning device is a heat exchanger.

In another embodiment according to any of the previous embodiments, theconditioning device is in communication with a high pressure compressor.

In another embodiment according to any of the previous embodiments, thehigh pressure compressor is axially downstream of the gearedarchitecture.

In another embodiment according to any of the previous embodiments, theconditioning device is radially outboard of a low pressure compressor.

In another embodiment according to any of the previous embodiments, thelow pressure compressor is downstream of the geared architecture.

In another embodiment according to any of the previous embodiments, thebearing structure is axially between the fan and the gearedarchitecture.

In another embodiment according to any of the previous embodiments, thefront center body case structure defines a core flow path for a coreairflow.

In another embodiment according to any of the previous embodiments,there are three turbine rotors, with a most downstream of the threeturbine rotors driving the geared architecture.

In another featured embodiment, the method of communicating a buffersupply air for a gas turbine engine includes communicating a buffersupply air across a core flow path, and communicating the buffer supplyair through a hollow front center body strut of a front center body casestructure which defines the core flow path, the hollow front center bodystrut within the core flow path.

In another embodiment according to the previous embodiment, furtherincluding communicating the buffer supply air to a bearing compartmentforward of a geared architecture.

In another embodiment according to the previous embodiment, furtherincluding, communicating the buffer supply air through a conditioningdevice upstream of the hollow front center body strut.

In another embodiment according to the previous embodiment, furtherincluding, communicating the buffer supply air to a bearing structuremounted to a front center body case structure which defines the coreflow path. The bearing structure rotationally supports a shaft driven bya geared architecture.

In another embodiment according to the previous embodiment, furtherincluding, driving a fan through the geared architecture. The bearingstructure is axially located between the fan and the gearedarchitecture.

In another featured embodiment, a method of communicating a buffersupply air for a gas turbine engine includes communicating a buffersupply air across a core flow path, communicating the buffer supply airto a bearing structure mounted to a front center body case structurewhich defines the core flow path, the bearing structure rotationallysupporting a shaft driven by a geared architecture, driving a fanthrough the geared architecture, the bearing structure axially locatedbetween the fan and the geared architecture, and communicating thebuffer supply air to a spinner supported by the fan.

BRIEF DESCRIPTION OF THE DRAWINGS

Various features will become apparent to those skilled in the art fromthe following detailed description of the disclosed non-limitingembodiment. The drawings that accompany the detailed description can bebriefly described as follows:

FIG. 1 is a schematic cross-section of a gas turbine engine;

FIG. 2 is an enlarged schematic cross-section of a sectional of the gasturbine engine;

FIG. 3 is a schematic view of a gas turbine engine with a bearingcompartment passage structure which bypasses around a gearedarchitecture; and

FIG. 4 is an enlarged schematic cross-section of a sectional of the gasturbine engine, which illustrates the bearing compartment passagestructure.

FIG. 5 shows another embodiment.

FIG. 6 shows yet another embodiment.

DETAILED DESCRIPTION

FIG. 1 schematically illustrates a gas turbine engine 20. The gasturbine engine 20 is disclosed herein as a two-spool turbofan thatgenerally incorporates a fan section 22, a compressor section 24, acombustor section 26 and a turbine section 28. Alternative engines mightinclude an augmentor section (not shown) among other systems orfeatures. The fan section 22 drives air along a bypass flowpath whilethe compressor section 24 drives air along a core flowpath forcompression and communication into the combustor section 26 thenexpansion through the turbine section 28. Although depicted as aturbofan gas turbine engine in the disclosed non-limiting embodiment, itshould be understood that the concepts described herein are not limitedto use with turbofans as the teachings may be applied to other types ofturbine engines such as a three-spool (plus fan) engine wherein anintermediate spool includes an intermediate pressure compressor (IPC)between the LPC and HPC and an intermediate pressure turbine (IPT)between the HPT and LPT.

The engine 20 generally includes a low spool 30 and a high spool 32mounted for rotation about an engine central longitudinal axis Arelative to an engine static structure 36 via several bearing structures38. The low spool 30 generally includes an inner shaft 40 thatinterconnects a fan 42, a low pressure compressor 44 (“LPC”) and a lowpressure turbine 46 (“LPT”). The inner shaft 40 drives the fan 42through a geared architecture 48 to drive the fan 42 at a lower speedthan the low spool 30. An exemplary reduction transmission is anepicyclic transmission, namely a planetary or star gear system.

The high spool 32 includes an outer shaft 50 that interconnects a highpressure compressor 52 (“HPC”) and high pressure turbine 54 (“HPT”). Acombustor 56 is arranged between the high pressure compressor 52 and thehigh pressure turbine 54. The inner shaft 40 and the outer shaft 50 areconcentric and rotate about the engine central longitudinal axis A whichis collinear with their longitudinal axes.

Core airflow is compressed by the low pressure compressor 44 then thehigh pressure compressor 52, mixed with the fuel and burned in thecombustor 56, then expanded over the high pressure turbine 54 and lowpressure turbine 46. The turbines 54, 46 rotationally drive therespective low spool 30 and high spool 32 in response to the expansion.

The engine shafts 40, 50 are supported at a plurality of points bybearing structures 38 within the engine static structure 36. In onenon-limiting embodiment, bearing structures 38 includes a #1 bearingstructure 38-1 forward of the gearbox 72 and a #2 bearing structure 38-2located aft of the gearbox 72.

With reference to FIG. 2, the engine static structure 36 proximate thecompressor section 24 generally includes a front center body casestructure 60 and an intermediate case structure 62 which mounts aft ofthe front center body case structure 60. It should be appreciated thatvarious case structures may alternatively or additionally be provided,yet benefit from the architecture described herein.

The front center body case structure 60 generally defines an annularcore flow path 64A for the core airflow into the low pressure compressor44. The intermediate case structure 62 defines the core flow path 64Baft of the core flow path 64A into the high pressure compressor 52 coreflow path 64C. The core flow path 64B is generally radially inward ofthe core flow path 64A to transition into the radially smaller diametercore flow path 64C. That is, the core flow path 64B generally defines a“wasp waist” gas turbine engine architecture.

The #2 bearing structure 38-2 at least partially supports the innershaft 40 relative to the front center body case structure 60. A #3bearing structure 38-3 generally supports the outer shaft 50 relativethe intermediate case structure 62. That is, the #2 bearing structure38-2 at least partially supports the low spool 30 and the #3 bearingstructure 38-3 at least partially supports the high spool 32. It shouldbe appreciated that various bearing systems such as thrust bearingstructures and mount arrangements will benefit herefrom.

A flex support 68 provides a flexible attachment of the gearedarchitecture 48 within the front center body case structure 60. The flexsupport 68 reacts the torsional loads from the geared architecture 48and facilitates vibration absorption as well as other support functions.A centering spring 70, which is a generally cylindrical cage-likestructural component with a multiple of beams that extend between flangeend structures, resiliently positions the #2 bearing structure 38-2 withrespect to the low spool 30. In one embodiment, the beams aredouble-tapered beams arrayed circumferentially to control a radialspring rate that may be selected based on a plurality of considerationsincluding, but not limited to, bearing loading, bearing life, rotordynamics, and rotor deflection considerations.

The gearbox 72 of the geared architecture 48 is driven by the low spool30 in the disclosed non-limiting embodiment through a coupling shaft 74.The coupling shaft 74 transfers torque through the #2 bearing structure38-2 to the gearbox 72 as well as facilitates the segregation ofvibrations and other transients. The coupling shaft 74 in the disclosednon-limiting embodiment includes a forward coupling shaft section 76 andan aft coupling shaft section 78. The forward coupling shaft section 76includes an interface spline 80 which mates with the gearbox 72. Aninterface spline 82 of the aft coupling shaft section 78 connects thecoupling shaft 74 to the low spool 30 through, in this non limitingembodiment, a low pressure compressor hub 84 of the low pressurecompressor 44.

A fan rotor bearing support structure 86 aft of the fan 42 extendsradially inward from the front center body case structure 60. The fanrotor bearing support structure 86 and the front center body casestructure 60 define a bearing compartment B-2. It should be appreciatedthat various bearing structures 38 and seals 88 may be supported by thefan rotor bearing support structure 86 to contain oil and supportrotation of an output shaft 100 which connects with the gearedarchitecture 48 to drive the fan 42.

The low pressure compressor hub 84 of the low pressure compressor 44includes a tubular hub 90 and a frustro-conical web 92. The tubular hub90 mounts to the inner shaft 40 through, for example, a splinedinterface adjacent to the #2 bearing structure 38-2. The frustro-conicalweb 92 extends in a forwardly direction from the tubular hub 90 axiallybetween the #2 bearing structure 38-2 and the #3 bearing structure 38-3.That is, the frustro-conical web 92 is axially located between thebearing structures 38-2, 38-3.

The #1 bearing structure 38-1 supports the output shaft 100 whichconnects the geared architecture 48 to the fan 42. The #1 bearingstructure 38-1 is located within a bearing compartment B-1 that isisolated by the geared architecture 48 from bearing compartment B-2.That is, the #1 bearing compartment B-1 is isolated from the engine coreaft of the geared architecture 48 and receives its buffer pressurizationsupply of buffer supply air through a #1 bearing compartment passagestructure 110 that crosses the annular core flow path 64A for the coreairflow into the low pressure compressor 44 (FIG. 3).

With reference to FIG. 4, the #1 bearing compartment passage structure110 is in communication with the core engine such as with the highpressure compressor 52 to supply a higher pressure bleed air flow ofbuffer supply air into the #1 bearing compartment B-1 such as the seal88-1 to, for example, pressurize the seal 88-1 and seal lubricatingfluid with respect to the #1 bearing structure 38-1. The buffer supplyair may be communicated from various other sources and may pass through,for example, a conditioning device 112 such as a buffer heat exchanger.The conditioning device 112 may further condition bleed flow C1, C2 fromthe high pressure compressor. It should be appreciated the various bleedsources from the high pressure compressor 52 may be selected through avalve 116.

The #1 bearing compartment passage structure 110 may be at leastpartially defined by a hollow front center body strut 60S of the frontcenter body case structure 60 to permit the buffer supply air to crossthe annular core flow path 64A without flow interference. That is, thebuffer supply air is communicated through the hollow front center bodystrut 60S and the core airflow passes around the hollow front centerbody strut 60S.

From the hollow front center body strut 60S, the buffer supply air iscommunicated through a passage 114 in the fan rotor bearing supportstructure 86 to, for example, the seal 88-1. It should be appreciatedthat various passages may alternatively or additionally be provided.

The passage of buffer supply air through the fan rotor bearing supportstructure 86 advantageously promotes heat transfer between the buffersupply air and the #1 bearing compartment B-1 to reduce buffer supplyair maximum temperate at high power condition and increases buffersupply air minimum temperatures at lower power settings. As the #1bearing structure 38-1 operates at a generally constant temperature, the#1 bearing compartment B-1 operates as a thermal ground with respect tothe buffer supply air.

Downstream of the #1 bearing compartment B-1, the buffer supply air maybe communicated in various manners for various usages such as toward thespinner 120 to facilitate spinner de-icing. The buffer supply air mayalternatively or additionally be ejected outward aft of the fan 42 torecirculate into the annular core flow path 64A to minimize any effectupon engine efficiency.

It should be understood that like reference numerals identifycorresponding or similar elements throughout the several drawings. Itshould also be understood that although a particular componentarrangement is disclosed in the illustrated embodiment, otherarrangements will benefit herefrom.

Although particular step sequences are shown, described, and claimed, itshould be understood that steps may be performed in any order, separatedor combined unless otherwise indicated and will still benefit from thepresent invention.

Although the different examples have specific components shown in theillustrations, embodiments of this invention are not limited to thoseparticular combinations. It is possible to use some of the components orfeatures from one of the examples in combination with features orcomponents from another one of the examples.

FIG. 5 shows an embodiment 200, wherein there is a fan drive turbine 208driving a shaft 206 to in turn drive a fan rotor 202. A gear reduction204 may be positioned between the fan drive turbine 208 and the fanrotor 202. This gear reduction 204 may be structured and operate likethe gear reduction disclosed above. A compressor rotor 210 is driven byan intermediate pressure turbine 212, and a second stage compressorrotor 214 is driven by a turbine rotor 216. A combustion section 218 ispositioned intermediate the compressor rotor 214 and the turbine section216.

FIG. 6 shows yet another embodiment 300 wherein a fan rotor 302 and afirst stage compressor 304 rotate at a common speed. The gear reduction306 (which may be structured as disclosed above) is intermediate thecompressor rotor 304 and a shaft 308 which is driven by a low pressureturbine section.

The foregoing description is exemplary rather than defined by thelimitations within. Various non-limiting embodiments are disclosedherein, however, one of ordinary skill in the art would recognize thatvarious modifications and variations in light of the above teachingswill fall within the scope of the appended claims. It is therefore to beunderstood that within the scope of the appended claims, the inventionmay be practiced other than as specifically described. For that reasonthe appended claims should be studied to determine true scope andcontent.

What is claimed:
 1. A turbofan engine comprising: a fan and an outer housing surrounding the fan to define a bypass duct; a low spool including an inner shaft; a high spool including an outer shaft, and wherein the inner shaft and the outer shaft are concentric and are rotatable about an engine central longitudinal axis; a compressor section including a low pressure compressor and a high pressure compressor axially aft of the low pressure compressor; a turbine section including a high pressure turbine and a fan drive turbine, the inner shaft driven by the fan drive turbine, and the outer shaft interconnecting the high pressure compressor and the high pressure turbine; a front center body case structure defining a first core flow path for core airflow into the low pressure compressor; an intermediate case structure defining a second core flow path for core airflow into the high pressure compressor, and the intermediate case structure mounted to an aft end of the front center body case structure; a geared architecture at least partially supported by the front center body case structure, and wherein the fan drive turbine drives the geared architecture to drive the fan at a speed lower than a speed of the fan drive turbine; a first bearing structure forward of the geared architecture, and said first bearing structure mounted to the front center body case structure to rotationally support a fan shaft that connects with the geared architecture to drive the fan; a fan rotor bearing support structure extending radially inward from said front center body case structure and at least partially supporting the first bearing structure; and a flex support that provides a flexible attachment of the geared architecture within the front center body case structure.
 2. The turbofan engine as recited in claim 1, wherein the geared architecture is an epicyclic transmission.
 3. The turbofan engine as recited in claim 2, further comprising a second bearing structure aft of the geared architecture.
 4. The turbofan engine as recited in claim 3, wherein the flex support reacts torsional loads from the geared architecture and facilitates vibration absorption in operation.
 5. The turbofan engine as recited in claim 4, further comprising: a coupling shaft between the fan drive turbine and the geared architecture; and wherein the coupling shaft transfers torque through the second bearing structure to the geared architecture in operation, and the coupling shaft facilitates segregation of vibrations in operation.
 6. The turbofan engine as recited in claim 5, further comprising a centering spring that resiliently positions the second bearing structure with respect to the low spool.
 7. The turbofan engine as recited in claim 4, wherein the first bearing structure includes a bearing located within a first bearing compartment that rotatably supports the fan shaft.
 8. The turbofan engine as recited in claim 7, further comprising: a bearing compartment passage structure in communication with the first bearing structure through the front center body case structure.
 9. The turbofan engine as recited in claim 8, wherein the first bearing compartment receives buffer supply air through the bearing compartment passage structure in operation.
 10. The turbofan engine as recited in claim 9, wherein the geared architecture is a star gear system.
 11. The turbofan engine as recited in claim 9, further comprising a third bearing structure at least partially supporting the outer shaft relative to the intermediate case structure.
 12. The turbofan engine as recited in claim 11, wherein the gear reduction is intermediate the low pressure compressor and the fan drive turbine such that the fan and the low pressure compressor rotate at a common speed.
 13. The turbofan engine as recited in claim 11, wherein: the front center body case structure includes a hollow front center body strut within the first core flow path; and the bearing compartment passage structure is at least partially defined by the hollow front center body strut such that the bearing compartment passage structure crosses the first core flow path.
 14. The turbofan engine as recited in claim 13, wherein the hollow front center body strut fluidly communicates with a passage of the fan rotor bearing support structure.
 15. The turbofan engine as recited in claim 14, further comprising: a coupling shaft between the fan drive turbine and the geared architecture; and wherein the coupling shaft transfers torque through the second bearing structure to the geared architecture in operation.
 16. The turbofan engine as recited in claim 15, wherein the coupling shaft facilitates segregation of vibrations in operation.
 17. The turbofan engine as recited in claim 16, wherein the coupling shaft includes an interface spline which mates with the geared architecture.
 18. The turbofan engine as recited in claim 16, wherein: the fan rotor bearing support structure and the front center body case structure define a second bearing compartment; and the second bearing compartment is axially aft of the geared architecture.
 19. The turbofan engine as recited in claim 18, wherein the gear reduction is intermediate the low pressure compressor and the fan drive turbine such that the fan and the low pressure compressor rotate at a common speed.
 20. The turbofan engine as recited in claim 18, wherein the first bearing compartment is isolated by the geared architecture from the second bearing compartment.
 21. The turbofan engine as recited in claim 10, wherein the bearing compartment passage structure communicates with the high pressure compressor to supply the buffer supply air into the first bearing compartment.
 22. The turbofan engine as recited in claim 20, wherein the geared architecture is a planetary gear system.
 23. The turbofan engine as recited in claim 20, wherein the geared architecture is a star gear system.
 24. The turbofan engine as recited in claim 23, wherein the low pressure compressor includes a low pressure compressor hub, the low pressure compressor hub includes a tubular hub and a frustro-conical web, the tubular hub is mounted to the inner shaft, and the frustro-conical web extends from the tubular hub such that the frustro-conical web is axially between the second bearing structure and the third bearing structure.
 25. The turbofan engine as recited in claim 23, wherein the second core flow path is generally radially inward of the first core flow path to transition into a radially smaller diameter core flow path through the high pressure compressor.
 26. The turbofan engine as recited in claim 25, further comprising a conditioning device in communication with the bearing compartment passage structure.
 27. The turbofan engine as recited in claim 26, wherein the conditioning device is a heat exchanger that conditions bleed flow from the compressor section.
 28. The turbofan engine as recited in claim 27, wherein the conditioning device conditions a first bleed flow and a second, different bleed flow, and the first bleed flow and the second bleed flow are provided by the high pressure compressor.
 29. The turbofan engine as recited in claim 28, wherein the first bleed flow and the second bleed flow are selected through a valve.
 30. The turbofan engine as recited in claim 29, wherein the conditioning device is radially outboard of the low pressure compressor. 